amdx wrote:
"nx7u" wrote in message
oups.com...

Yes to both.
A corner-fed patch is roughly circularly polarized...I say roughly
because there are some other pertubations typically made to force the
sense of the CP, and also to improve the circularity.
But if the feed is just offset a bit (like 1/4-3/4 rather than
1/2-1/2)...well that should act similarly to an offset-fed dipole, so
you'd have higher input impedance and some feedpoint reactance. And
the pattern linearity would be more elliptical (patches typically have
relatively high crosspolar response anyway).


Ok, to make sure I understand;
If I put the feed on the lowerhalf of the patch the antenna would be
vertically polarized?
And, if I put the feed on the left or right half of the patch the antenna
would be horizontally polarized?
Now to complicate things, I see some patches split the difference and put
the feedpoint on the left side of the lowerhalf. What does that do?
Thanks, Mike

My next trick is to put 4 Patch antennas on one plate, I'm looking for the
proper
spacing between Patches. My guide at this point is this site,
http://www.darc.de/distrikte/g/T_ATV...d-Array-GB.pdf
the author puts 4 biquads on one plate with proper phaseing and impedance
matching.
The author uses .8 wavelength vertical and .9 wavelength horizontal
spacing betwen centers.
I'm thinking 1.0 wavelength between centers is correct, but open to some
correction factor
for some (unknown to me) characteristic.
Any help and leads appreciated,
Thanks. Mike



You can space patches quite closely or far apart. It typically depends
on how hard you want to work on your feed network, because closer
spacing increases the mutual coupling, which makes it harder to get the
right phasing. OTOH, spacing them too far apart gives you grating lobes
in the pattern. 1 wavelength is quite far. Consider, for instance,
that most patch antennas are on some sort of substrate with an
epsilon1, so the actual patch size is substantially smaller than a free
space halfwavelength. If your substrate epsilon were, say, 2.2, then
the patch would be roughly 0.5/sqrt(2.2) or about 0.34 lambda(freespace)
on a side. At this size, spacing them on half wavelength centers would
be easy.

Some other aspects that might drive how you lay out the patch array is
how you intend to feed them. If you're feeding them with a microstrip
on the edge, then you have to find room for the feedline on the top and
the feed network. If you feed them from the bottom (probe feed) it's a
bit easier to build your feed network on the back side. You can also
slot feed the patches.